Nickel-Catalyzed Suzuki Cross Couplings with Unprotected Allylic Alcohols Enabled by Bidentate N-Heterocyclic Carbene (NHC)/Phosphine Ligands

ACS Catalysis, Journal Year: 2017, Volume and Issue: 8(1), P. 86 - 89

Published: Nov. 17, 2017

Cross couplings between simple allylic alcohols and aryl vinyl boronic acids are efficiently catalyzed by nickel(0) catalysts bidentate N-heterocyclic carbene/phosphine ligands. The nature of the ligand is shown to extend catalyst lifetime enable high yields corresponding cross-coupling products. X-ray crystallography confirms scaffold. Multistep cross coupling-alkene/alkyne insertions reactions also conducted substrate makes pendant phosphine unnecessary.

Language: Английский

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The Important Role of the Byproduct Triphenylphosphine Oxide in the Magnesium(II)‐Catalyzed Enantioselective Reaction of Hemiacetals and Phosphorus Ylides

Angewandte Chemie International Edition, Journal Year: 2018, Volume and Issue: 57(29), P. 9088 - 9092

Published: May 16, 2018

By employing a simple in situ generated magnesium catalyst, direct asymmetric reaction between hemiacetals and phosphorus ylides was achieved through tandem Wittig-oxa-Michael sequence. Enantioenriched chromans, isochromans, tetrahydropyrans were obtained good chemical yields, (-)-erythrococcamide B synthesized enantioenriched form. The byproduct triphenylphosphine oxide identified as necessary additive for this process.

Language: Английский

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Stereoselective Synthesis of Piperidines by Iridium-Catalyzed Cyclocondensation

Angewandte Chemie International Edition, Journal Year: 2017, Volume and Issue: 56(38), P. 11515 - 11519

Published: July 21, 2017

Abstract An iridium‐catalyzed cyclocondensation of amino alcohols and aldehydes is reported. Intramolecular allylic substitution by an enamine intermediate subsequent in situ reduction furnishes 3,4‐disubstituted piperidines with high enantiospecificity good diastereoselectivity. The modular approach the broad functional group tolerance provide access to diverse piperidine derivatives, which were further functionalized give a versatile set products.

Language: Английский

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Tsuji–Trost Reaction of Non‐Derivatized Allylic Alcohols

Chemistry - A European Journal, Journal Year: 2017, Volume and Issue: 24(14), P. 3488 - 3498

Published: Nov. 27, 2017

Abstract Palladium‐catalyzed allylic substitution of non‐derivatized enantioenriched alcohols with a variety uncharged N‐, S‐, C‐ and O‐centered nucleophiles using bidentate BiPhePhos ligand is described. A remarkable effect the counter ion (X) XPd[κ 2 ‐BiPhePhos][η 3 ‐C H 5 ] was observed. When ClPd[κ (complex I ) used as catalyst, non‐reproducible results were obtained. Study complex by X‐ray crystallography, 31 P NMR spectroscopy, ESI‐MS showed that decomposition occurred where one phosphite ligands oxidized to corresponding phosphate, generating 1 ‐BiPhePhosphite‐phosphate][η species II ). chloride exchanged weaker coordinating OTf − more stable Pd[κ + +[OTf] III formed. Complex performed better gave higher enantiospecificities in reactions. evaluated Tsuji–Trost reactions stereogenic alcohols. The desired products obtained good excellent yields (71–98 %) (73–99 for both inter‐ intramolecular only water generated by‐product. methodology applied key steps total synthesis ( S )‐cuspareine (+)‐lentiginosine. reaction mechanism involving palladium hydride intermediate activation hydroxyl group proposed overall transformation.

Language: Английский

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Rhodium‐Catalyzed Asymmetric Intramolecular Hydroamination of Allenes

Angewandte Chemie International Edition, Journal Year: 2019, Volume and Issue: 58(29), P. 9994 - 9997

Published: May 15, 2019

Abstract The rhodium‐catalyzed asymmetric intramolecular hydroamination of sulfonyl amides with terminal allenes is reported. It provides selective access to 5‐ and 6‐membered N ‐heterocycles, scaffolds found in a large range different bioactive compounds. Moreover, gram scale reactions, as well the application suitable product transformations natural products key intermediates thereof are demonstrated.

Language: Английский

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A Versatile Synthesis of Vinyl-Substituted Heterocycles via Regio- and Enantioselective Pd-Catalyzed Tandem Allylic Substitution

Organic Letters, Journal Year: 2020, Volume and Issue: 22(11), P. 4483 - 4488

Published: May 26, 2020

We herein report a versatile, regio- and enantioselective palladium-catalyzed tandem allylic substitution powered by chiral bisphosphorus ligand WingPhos with the palladium loading as low 0.1 mol %, forming series of vinyl-substituted heterocycles, including tetrahydroquinoxalines, piperazines, dihydro-2H-benzo[b][1,4]-oxazines, morpholines, in exellent ee's yields. The protocol features readily available starting materials, mild reaction conditions, broad substrate scope. Mechanistic investigation supports process.

Language: Английский

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Iridium‐Catalyzed Asymmetric Allylic Dearomatization by a Desymmetrization Strategy

Angewandte Chemie, Journal Year: 2017, Volume and Issue: 129(47), P. 15289 - 15293

Published: Oct. 5, 2017

Abstract A desymmetrization strategy was developed involving iridium‐catalyzed allylic dearomatization of indoles. The six‐membered‐ring spiroindolenines contain three contiguous stereogenic centers, including an all‐carbon quaternary center, and were obtained in up to 99 % yield with ee >95:5 d.r. When treated a catalytic amount tosylic acid, six‐membered spiroindolenine undergoes unprecedented six‐to‐seven‐membered ring expansion, affording the corresponding hexahydroazepino[4,5‐ b ]indole.

Language: Английский

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Morpholine Ketene Aminal as Amide Enolate Surrogate in Iridium‐Catalyzed Asymmetric Allylic Alkylation

Angewandte Chemie International Edition, Journal Year: 2019, Volume and Issue: 58(28), P. 9537 - 9541

Published: May 9, 2019

Abstract Morpholine ketene aminal is employed in iridium‐catalyzed asymmetric allylic alkylation reactions as a surrogate for amide enolates to prepare γ,δ‐unsaturated β‐substituted morpholine amides. Kinetic resolution or, alternatively, stereospecific substitution affords the corresponding products high enantiomeric excess. The utility of generated by this method has been showcased their further elaboration into amines, ketones, or acyl silanes. A putative catalytic intermediate (η 3 ‐allyl)iridium(III) with achiral P,Olefin‐ligand was synthetized and characterized first time.

Language: Английский

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Total Synthesis of (−)-Geissoschizol through Ir-Catalyzed Allylic Amidation as the Key Step

Organic Letters, Journal Year: 2017, Volume and Issue: 19(23), P. 6460 - 6462

Published: Nov. 2, 2017

The iridium-catalyzed, Zn(OTf)2 promoted asymmetric allylic amidation of a secondary alcohol derived from tryptamine has been utilized to forge tetrahydro-β-carboline. Based on this key step, novel, facile, and enantioselective total synthesis (-)-geissoschizol was achieved in 10 steps.

Language: Английский

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Enantioselective Intramolecular Nicholas Reaction Catalyzed by Chiral Phosphoric Acid: Enantioconvergent Synthesis of Seven‐Membered Cyclic Ethers from Racemic Diols

Angewandte Chemie International Edition, Journal Year: 2018, Volume and Issue: 57(42), P. 13917 - 13921

Published: Aug. 30, 2018

An enantioconvergent intramolecular Nicholas reaction of racemic diols was developed using BINOL- and SPINOL-derived phosphoric acids as the chiral Brønsted acid catalyst. The features an efficient approach to synthesis seven-membered cyclic ethers in a highly enantioselective manner. Further derivatization enantioenriched ethers, initiated by de-complexation dicobalt species, afforded densely functionalized having unsaturated diester moiety without loss enantiomeric excess.

Language: Английский

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